This invention relates to organic salt compositions useful in the preparation of organoclay compositions, polymer-organoclay composite compositions, and methods for the preparation of polymer nanocomposites.
Organoclays serve as useful additives in the preparation of polymer compositions possessing enhanced physical properties relative to unfilled polymeric materials, and relative to polymer composite compositions comprising inorganic clays. Organoclays are typically prepared by replacing the inorganic cations present in the galleries between the silicate layers of a typical inorganic clay with organic cations. A principal advantage of the organoclay compositions is that when they are combined within a polymer composition the organoclay is found to exfoliate and interact with the polymer matrix to a greater degree than in the case of a corresponding composition comprising a purely inorganic clay. The presence of organic moieties between the inorganic silicate layers present in the organoclay both swells the organoclay, i.e. increases the d-spacing in the organoclay relative to the d-spacing in the corresponding inorganic clay, and enhances the tendency of the organoclay to exfoliate when subjected to shearing forces within a polymer matrix. In some instances exfoliation occurs so completely that a polymeric composition comprising very highly dispersed silicate layers results, and the organoclay-containing polymer composition is referred to as a nanocomposite.
Despite impressive advances in this field over the past decade, improved organoclay compositions are actively sought after and are highly prized when discovered. One deficiency in many organoclays is the thermal instability of the organic cation(s) present, making them unsuitable in applications wherein the polymer-organoclay composition must be processed at high temperature, as is the case in organoclay-containing polymer compositions comprising “high heat” polymers such as polyetherimide. Another deficiency of many known organoclay compositions is that the organoclay compositions may interact unfavorably with the polymer matrix when the organoclay composition is dispersed in a polymer matrix and marginal performance of the organoclay-containing polymer composition may result. For example, when the organic cation is a primary ammonium cation and the polymer matrix is sensitive to amine groups, degradation of the polymer matrix may result during melt mixing, for example, of the polymer matrix with the organoclay composition.
Thus, there is keen interest in the development of organoclay compositions which are both thermally stable and which interact favorably with the polymer matrix in organoclay-containing polymer compositions. The instant invention addresses these and other technical challenges.